Modified Organosolv A Fractionation Process of Lignocellulosic Biomass for Co-Production of Fuels and Chemicals

W.J.J. Huijgen R.R. van der Laan J.H. Reith

Presented at the 4th International Conference on Renewable Resources & Biorefineries, 1-4 June 2008, Rotterdam, The Netherlands

ECN-L--08-057 June 2008

MODIFIED ORGANOSOLV

A Fractionation Process of Lignocellulosic Biomass for Co-production of Fuels and Chemicals Wouter Huijgen, Ron van der Laan & Hans Reith Contents

Introduction • Biomass pre-treatment • Organosolv

Experimental Results • Influence process conditions • Alternative solvents

• Catalysts

• characterisation

Conclusions

02/06/2008 2 Biorefinery

Primary biorefinery Secondary biorefinery

Ethanol Fermentation Butanol Propanediol Lactic acid Enzymatic hydrolysis Conversion Lignocellulosic Chemical derivatives, & biomass & PretreatmentPretreatment e.g. surfactants Hemi- synthesis && cellulose residual streams fractionationfractionation Platform chemicals, Thermochemical Lignin e.g. phenolics, styrene,… depolymerisation Performance products & conversion Fuel additives Electricity H/P Heat

Goals primary biorefinery: • Enhancement (enzymatic) degradability of cellulose to fermentable sugars. • Hemicellulose hydrolysis to sugars. • Extraction of high-quality lignin for production of chemicals.

Æ Fractionation of all biomass fractions in a sufficient quality for production of (bio)chemicals.

02/06/2008 3 Biomass pre-treatment

Pre-treatment technologies • Many pre-treatment technologies: steam explosion, ammonia fibre explosion (AFEX), acid hydrolysis, alkaline

pre-treatment, etc. • Different functionalities and characteristics. • Comparison of technologies Æ selection of organosolv

Why organosolv? • Other pretreatments generally produce low quality lignin, only suitable for CHP. • Avoidance waste generation (due to neutralization).

• Minimization formation of fermentation inhibitors.

02/06/2008 4 Organosolv process Solvent recycling

Lignocellulosic biomass Lignin Solvent Organic solvent Organosolv Hemicellulose (aq) separation separation Water (+ catalyst)

Cellulose (S) Lignin (S) (to enzymatic hydrolysis)

• Typical process conditions (ECN): 160-200 °C, 15-60 min, 5-30 bar. • Possible solvents: (standard), , , , dioxane, etc.

R&D challenges: • Organosolv process developed in 70-80’s as alternative pulping process. • Applicability for biorefinery purposes? Adaptations required? • Reduction of costs and energy consumption (solvent recycling).

02/06/2008 5 Experimental set-up Analysis Washing / composition Milling drying Solid residue Enzymatic hydrolysis (Genencor GC220, Biomass Filtration 69h, 50°C, pH 5)

Filtrate Analysis sugars (HPLC) (monomeric Solvent / + oligomeric) H2O Analysis Optional: inhibitors (GC-MS) Volume: 0.5 / 2 ltr catalyst Stirring Lignin precipitation Temperature ↑ by water addition

02/06/2008 6 Effects on Biomass Fresh material (left), pre-treated (right): • General: colour gets darker. • Structural changes: – Function of temperature and stirring rate (mechanical impact). – ‘’ like appearance.

Poplar wood

Wheat straw

Wheat straw Stirring rate: Low (100 rpm) High (500 rpm) Fibres ‘Cardboard’ T = 200 °C, solvent: ethanol/water.

02/06/2008 7 (Hemi)Cellulose Hydrolysis – Effect of Temperature

Cumulative hydrolysis during pre-treatment and enzymatic hydrolysis:

Glucose (incl oligomers) Xylose (incl oligomers) 100 100 Enzymatic Enzymatic Pre-treatment Pre-treatment 80 80

60 60

40 40 Hydrolysis [%] Hydrolysis [%] 20 20

0 0 Fresh willow 160 190 200 Fresh willow 160 190 200 Temperature [°C] Temperature [°C] Willow • Temperature key process parameter. EtOH:H2O 60:40 wt% • Cellulose hydrolysis during pre-treatment negligible, hemicellulose ±20%. 60 min No catalyst • Large enhancement of enzymatic hydrolysis cellulose (max ±75%). 500 rpm • Inhibitor formation: increase with temperature, high (≥200 °C).

02/06/2008 8 Scanning Electron Micrographs

Fresh willow Pre-treated willow (190°C, 60 min, 60wt% EtOH)

• Cellulose fibrous structure remains intact • Extraction of hemicellulose and lignin • More open structure Æ better access for enzymes

02/06/2008 9 (Hemi)Cellulose Hydrolysis - EtOH:H2 O ratio

Cumulative hydrolysis during pre-treatment and enzymatic hydrolysis:

100 Enzymatic 100 Pre-treatment 80 80 Willow 190°C 60 60 60 min No catalyst 40 40 500 rpm Hydrolysis [%] Hydrolysis Hydrolysis [%]

20 20

0 0 30 60 90 30 60 90 Composition solvent [wt% EtOH] Composition solvent [wt% EtOH]

• Large effect on hemicellulose hydrolysis during pre-treatment.

• Enzymatic degradability cellulose remains similar at low EtOH:H2O ratio.

02/06/2008 10 Extraction of Lignin – EtOH:H2 O ratio

40 Pre-treated willow 30 20 g/L (ECN) Fresh willow 35 40 g/L (ECN) 25 20 g/L (Ni et al.) 30 20 25

20 15

15 10 10

Lignin dissolved [g/L] 5 5 Lignin content in solids [wt%]

0 0 0 20406080100 0 20406080100

Composition solvent [wt% EtOH] Composition solvent [wt% EtOH]

• Ethanol:water ratio solvent major influence delignification (opt 60 wt% EtOH).

• Delignification optimum at higher EtOH-H2O ratio, in contrast to hemicellulose hydrolysis.

• Solubility of lignin (fragments) dependent on solvent mixture composition.

02/06/2008 11 Lignin extraction and recovery – Temperature

100

80 Lignin degradation / mass losses Willow 60 Lignin extracted EtOH:H O 60:40 wt% (freeze dried) 2 40 60 min Lignin in solid No catalyst

Distribution [%] 20 500 rpm

0 Fresh 160 190 200 willow

Reaction temperature [°C]

• Substantial delignification of willow wood achieved (max ±70%). • Similarly to hydrolysis: temperature key process parameter & degradation (inhibitor formation) significant at ≥200°C. • Separation of lignin from filtrate possible by precipitation. • Delignification at milder process conditions Æ alternative solvents & catalysts.

02/06/2008 12 Alternative solvents

• Solvents known as good lignin solvents tested. • Colour and structure of biomass indicative for enhanced delignification wheat straw. Ethanol Acetone • However, differences in conversion and amount of lignin precipitated small.

Precipitated lignin ] 80 Solid residue 70 60 Wheat straw Dioxane 50

40 Cellulose content Wheat straw 30 feedstock Lignin content 60:40 wt% solvent:water 20 feedstock 200 °C 10 30 min Amount [wt% starting material 0 100 rpm Ethanol Acetone Dioxane Solvent

02/06/2008 13 Effect of Catalysts

Screening: • Addition of acids effective. Lignin precipitated 80% • H SO most effective. Solid residue 2 4 70% • NaOH not effective due to

60% neutralisation (at this concentration).

50% • MgCl2 potentially interesting catalyst since it does not lower the pH by 40% itself. 30%

20%

10% Willow Amount [wt% starting material] starting [wt% Amount 60:40 wt% EtOH-water 0% None H2SO4 HCl H3PO4 NaOH MgCl2 200 °C 30 min Catalyst 100 rpm 0.025M catalyst

02/06/2008 14 Catalyst – H2 SO4

80% Lignin precipitated

70% Solid residue

60% 50% Willow 40% Cellulose content of 60:40 wt% EtOH-water willow feedstock 200 °C 30% 30 min 20% 100 rpm

10% Amount [wt% starting material] starting [wt% Amount 0% 0.000 0.010 0.025 0.033 Concentration [mol/L]

• Hemicellulose hydrolysis and delignification are improved. • Up to 2/3 of lignin isolated (i.e., extracted and precipitated). • At high concentrations: even cellulose hydrolysis. • Not required (and high formation of inhibitors and higher costs)

02/06/2008 15 Lignin characterisation

Performed by A&F (NL) & VTT (FI). Feedstock / Mw PD sample • Lignin produced relatively pure (94-100 wt%). Poplar 2419 3.5 • Main contaminant: xylose (mostly oligomers). Barley straw 3006 4.1 Willow 3452 4.1 Alcell® 2985 3.6 • Mean molecular weight (MW) and polydispersity (PD): – Comparable with commercial organosolv lignin.

– Low relative to other types of .

• Mean lignin particle size (volume-based): 61 μm (poplar) and 10 μm (wheat straw).

• Further characterisation in progress.

• Purity and MW distribution indicate suitability of lignin for chemical production. • Conversion tests of lignin into e.g. phenols to be performed.

02/06/2008 16 Conclusions

• Organosolv suitable for fractionation within biorefinery: – Hemicellulose hydrolysis (max ±80%). – Delignification (max ± 70%). • Cellulose fraction: enzymatic degradability strongly enhanced.

– Enhancement of enzymatic degradability (max ± 75%). • Lignin seems of sufficient quality for chemicals production.

Further R&D: • Process optimization: particularly higher delignification at milder process conditions.

• Further characterization of lignin & conversion to products. • Conceptual process design.

02/06/2008 17 Thank you for your attention!

More information: [email protected] www.ecn.nl/bkm/

This work is in part performed in the context of:

SenterNovem EOS-LT

02/06/2008 18